If you create a grouping view for a grid, and enable the grouping display, the group is not rendered for the region that you have to scroll to (see screenshot).

I provide a patch file against your explorer code to reproduce. I changed entry point to go straight to this example, since explorer framework was making it difficult for me to create a scrolling grid.

Once pages loads, expand the "Change Column" as far as you can. Then expand the "Price" Column, this will force the scroll bar to render.